Molding and separating of bulk-solidifying amorphous alloys and composite containing amorphous alloy

ABSTRACT

A method to form and to separate bulk solidifying amorphous alloy or composite containing amorphous alloy where the forming and separating takes place at a temperature around the glass transition temperature or within the super cooled liquid region are provided.

FIELD OF THE INVENTION

The present invention relates to molding and separating ofbulk-solidifying amorphous alloys and composite containing amorphousalloy for the manufacture of bulk-solidifying amorphous alloys andmethods of making the same.

BACKGROUND

A large portion of the metallic alloys in use today are processed bysolidification casting, at least initially. The metallic alloy is meltedand cast into a metal or ceramic mold, where it solidifies. The mold isstripped away, and the cast metallic piece is ready for use or furtherprocessing. The as-cast structure of most materials produced duringsolidification and cooling depends upon the cooling rate. There is nogeneral rule for the nature of the variation, but for the most part thestructure changes only gradually with changes in cooling rate. On theother hand, for the bulk-solidifying amorphous alloys, the changebetween the amorphous state produced by relatively rapid cooling and thecrystalline state produced by relatively slower cooling is one of kindrather than degree—the two states have distinct properties.

A conventional method for making a bulk-metallic glass (BMG) partrequires casting a block of material at or above the melting temperatureof the amorphous metal alloy in a mold, freezing the molten amorphousmetal alloy in the mold to form a cast block, and then using a cuttingtool to remove the gate portion of the cast block and shape the castblock into the desired final geometry. However, casting requires meltingand cooling of the amorphous metal alloy, which can cause uncontrolledamount of amorphicity in the BMG part. Furthermore, the post-processingcost for removing the gate and runner overflow and shaping the castblock into the desired final part geometry can be quite high. Therefore,new methods for making BMG parts that overcome the above mentionedlimitations of the casting process are desirable.

SUMMARY

The embodiments herein are directed to a hot forming and hot separatingprocess for bulk-solidifying amorphous alloys which takes place in thesupercooled liquid region or around glass transition temperature.

The embodiments herein relate to combining casting/molding of a BMGalloy into a BMG part and post-processing of the BMG part in anintegrated operation without cooling the BMG part to room temperature ornear room temperature, whereas conventional processes requirecasting/molding of a BMG alloy into a BMG part, cooling the BMG part tonear room temperature and subsequent post-processing of the BMG part.

One embodiment herein relates to an injection molding system that doesnot require melting the BMG material and cutting a portion of a moldedBMG part using a hot knife without cooling the molded BMG part to roomtemperature. This embodiment relates to molding a BMG part at atemperature in the supercooled liquid region of the BMG material in theTTT diagram and then degating the part at that temperature. For example,one could heat up the BMG material between Tg and Tx within thesupercooled liquid region of the TTT diagram of the BMG material to atemperature where the BMG material is flowable, apply pressure to theheated, flowable BMG material, fill a mold with the flowable BMGmaterial, and then create a part having the desired final geometrydirectly in the mold. So, instead of casting the amorphous alloy onewould be molding it at a temperature in the supercooled liquid region ofthe amorphous alloy.

Another embodiment relates to using a casting or molding machine to castor mold a BMG part at or near the melting temperature of the BMGmaterial, cooling the BMG material to below Tg to form a BMG part, andthen using a hot knife to degate and remove the gate and the runner fromthe BMG part at a temperature in the supercooled liquid region of theBMG material in the TTT diagram. This embodiment relates to using acutting tool that could be heated to a temperature between Tg and Tx andincorporating the cutting tool into the mold of the molding system tocut the gate, runner and other extraneous portions of the molded partright after molding instead of waiting for the molded part to cool downto room temperature and then using conventional tools like a saw orwater jet to degate the gate and runner from the molded part. Forexample, one could cast an exemplar BMG alloy by heating it to above themelting temperature at about 1100 degree C. and injecting the molten BMGalloy into a mold, cooling the molten BMG alloy in the mold to about300-350 degree C. to form a BMG part, and using a hot knife heated toabout 450 degree C. and embedded in the mold to shear off portions (suchas the date and runner) of the BMG part. This way, one would combine thesteps of casting or molding and post-processing cutting off portions ofthe BMG part without cooling the BMG part all the way down to roomtemperature, thereby conserving energy, improving the speed of theprocess, and getting more improved cuts by shearing the BMG part using ahot knife.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides a temperature-viscosity diagram of an exemplary bulksolidifying amorphous alloy.

FIG. 2 provides a schematic of a time-temperature-transformation (TTT)diagram for an exemplary bulk solidifying amorphous alloy.

FIGS. 3( a) and 3(b) provide a schematic of different exemplaryembodiments of molding and casting systems. The bulk amorphous alloy hasa critical thickness of (a) and the final part has the smallestdimension that is thicker than the critical thickness (>a). Cuttingtool, bulk amorphous alloy or composite containing amorphous alloy, andthe mold are heated to around transition temperature or within thesupercooled liquid region by any mean.

FIGS. 4( a) and 4(b) provide a schematic of different exemplaryembodiments of forming microfeatures on a surface of a BMG part duringcutting of the BMG part.

DETAILED DESCRIPTION

All publications, patents, and patent applications cited in thisSpecification are hereby incorporated by reference in their entirety.

The articles “a” and “an” are used herein to refer to one or to morethan one (i.e., to at least one) of the grammatical object of thearticle. By way of example, “a polymer resin” means one polymer resin ormore than one polymer resin. Any ranges cited herein are inclusive. Theterms “substantially” and “about” used throughout this Specification areused to describe and account for small fluctuations. For example, theycan refer to less than or equal to ±5%, such as less than or equal to±2%, such as less than or equal to ±1%, such as less than or equal to±0.5%, such as less than or equal to ±0.2%, such as less than or equalto ±0.1%, such as less than or equal to ±0.05%.

Bulk-solidifying amorphous alloys, or bulk metallic glasses (“BMG”), area recently developed class of metallic materials. These alloys may besolidified and cooled at relatively slow rates, and they retain theamorphous, non-crystalline (i.e., glassy) state at room temperature.Amorphous alloys have many superior properties than their crystallinecounterparts. However, if the cooling rate is not sufficiently high,crystals may form inside the alloy during cooling, so that the benefitsof the amorphous state can be lost. For example, one challenge with thefabrication of bulk amorphous alloy parts is partial crystallization ofthe parts due to either slow cooling or impurities in the raw alloymaterial. As a high degree of amorphicity (and, conversely, a low degreeof crystallinity) is desirable in BMG parts, there is a need to developmethods for casting BMG parts having controlled amount of amorphicity.

FIG. 1 (obtained from U.S. Pat. No. 7,575,040) shows aviscosity-temperature graph of an exemplary bulk solidifying amorphousalloy, from the VIT-001 series of Zr—Ti—Ni—Cu—Be family manufactured byLiquidmetal Technology. It should be noted that there is no clearliquid/solid transformation for a bulk solidifying amorphous metalduring the formation of an amorphous solid. The molten alloy becomesmore and more viscous with increasing undercooling until it approachessolid form around the glass transition temperature. Accordingly, thetemperature of solidification front for bulk solidifying amorphousalloys can be around glass transition temperature, where the alloy willpractically act as a solid for the purposes of pulling out the quenchedamorphous sheet product.

FIG. 2 (obtained from U.S. Pat. No. 7,575,040) shows thetime-temperature-transformation (TTT) cooling curve of an exemplary bulksolidifying amorphous alloy, or TTT diagram. Bulk-solidifying amorphousmetals do not experience a liquid/solid crystallization transformationupon cooling, as with conventional metals. Instead, the highly fluid,non crystalline form of the metal found at high temperatures (near a“melting temperature” Tm) becomes more viscous as the temperature isreduced (near to the glass transition temperature Tg), eventually takingon the outward physical properties of a conventional solid.

Even though there is no liquid/crystallization transformation for a bulksolidifying amorphous metal, a “melting temperature” Tm may be definedas the thermodynamic liquidus temperature of the correspondingcrystalline phase. Under this regime, the viscosity of bulk-solidifyingamorphous alloys at the melting temperature could lie in the range ofabout 0.1 poise to about 10,000 poise, and even sometimes under 0.01poise. A lower viscosity at the “melting temperature” would providefaster and complete filling of intricate portions of the shell/mold witha bulk solidifying amorphous metal for forming the BMG parts.Furthermore, the cooling rate of the molten metal to form a BMG part hasto such that the time-temperature profile during cooling does nottraverse through the nose-shaped region bounding the crystallized regionin the TTT diagram of FIG. 2. In FIG. 2, Tnose is the criticalcrystallization temperature Tx where crystallization is most rapid andoccurs in the shortest time scale.

The supercooled liquid region, the temperature region between Tg and Txis a manifestation of the extraordinary stability againstcrystallization of bulk solidification alloys. In this temperatureregion the bulk solidifying alloy can exist as a high viscous liquid.The viscosity of the bulk solidifying alloy in the supercooled liquidregion can vary between 10¹² Pa s at the glass transition temperaturedown to 10⁵ Pa s at the crystallization temperature, the hightemperature limit of the supercooled liquid region. Liquids with suchviscosities can undergo substantial plastic strain under an appliedpressure. The embodiments herein make use of the large plasticformability in the supercooled liquid region as a forming and separatingmethod.

One needs to clarify something about Tx. Technically, the nose-shapedcurve shown in the TTT diagram describes Tx as a function of temperatureand time. Thus, regardless of the trajectory that one takes whileheating or cooling a metal alloy, when one hits the TTT curve, one hasreached Tx. In FIG. 1 (b), Tx is shown as a dashed line as Tx can varyfrom close to Tm to close to Tg.

The schematic TTT diagram of FIG. 2 shows processing methods of diecasting from at or above Tm to below Tg without the time-temperaturetrajectory (shown as (1) as an example trajectory) hitting the TTTcurve. During die casting, the forming takes place substantiallysimultaneously with fast cooling to avoid the trajectory hitting the TTTcurve. The processing methods for superplastic forming (SPF) from at orbelow Tg to below Tm without the time-temperature trajectory (shown as(2), (3) and (4) as example trajectories) hitting the TTT curve. In SPF,the amorphous BMG is reheated into the supercooled liquid region wherethe available processing window could be much larger than die casting,resulting in better controllability of the process. The SPF process doesnot require fast cooling to avoid crystallization during cooling. Also,as shown by example trajectories (2), (3) and (4), the SPF can becarried out with the highest temperature during SPF being above Tnose orbelow Tnose, up to about Tm. If one heats up a piece of amorphous alloybut manages to avoid hitting the TTT curve, you have heated “between Tgand Tm”, but one would have not reached Tx.

Typical differential scanning calorimeter (DSC) heating curves ofbulk-solidifying amorphous alloys taken at a heating rate of 20 C/mindescribe, for the most part, a particular trajectory across the TTT datawhere one would likely see a Tg at a certain temperature, a Tx when theDSC heating ramp crosses the TTT crystallization onset, and eventuallymelting peaks when the same trajectory crosses the temperature range formelting. If one heats a bulk-solidifying amorphous alloy at a rapidheating rate as shown by the ramp up portion of trajectories (2), (3)and (4) in FIG. 2, then one could avoid the TTT curve entirely, and theDSC data would show a glass transition but no Tx upon heating. Anotherway to think about it is trajectories (2), (3) and (4) can fall anywherein temperature between the nose of the TTT curve (and even above it) andthe Tg line, as long as it does not hit the crystallization curve. Thatjust means that the horizontal plateau in trajectories might get muchshorter as one increases the processing temperature.

Phase

The term “phase” herein can refer to one that can be found in athermodynamic phase diagram. A phase is a region of space (e.g., athermodynamic system) throughout which all physical properties of amaterial are essentially uniform. Examples of physical propertiesinclude density, index of refraction, chemical composition and latticeperiodicity. A simple description of a phase is a region of materialthat is chemically uniform, physically distinct, and/or mechanicallyseparable. For example, in a system consisting of ice and water in aglass jar, the ice cubes are one phase, the water is a second phase, andthe humid air over the water is a third phase. The glass of the jar isanother separate phase. A phase can refer to a solid solution, which canbe a binary, tertiary, quaternary, or more, solution, or a compound,such as an intermetallic compound. As another example, an amorphousphase is distinct from a crystalline phase.

Metal, Transition Metal, and Non-Metal

The term “metal” refers to an electropositive chemical element. The term“element” in this Specification refers generally to an element that canbe found in a Periodic Table. Physically, a metal atom in the groundstate contains a partially filled band with an empty state close to anoccupied state. The term “transition metal” is any of the metallicelements within Groups 3 to 12 in the Periodic Table that have anincomplete inner electron shell and that serve as transitional linksbetween the most and the least electropositive in a series of elements.Transition metals are characterized by multiple valences, coloredcompounds, and the ability to form stable complex ions. The term“nonmetal” refers to a chemical element that does not have the capacityto lose electrons and form a positive ion.

Depending on the application, any suitable nonmetal elements, or theircombinations, can be used. The alloy (or “alloy composition”) cancomprise multiple nonmetal elements, such as at least two, at leastthree, at least four, or more, nonmetal elements. A nonmetal element canbe any element that is found in Groups 13-17 in the Periodic Table. Forexample, a nonmetal element can be any one of F, Cl, Br, I, At, O, S,Se, Te, Po, N, P, As, Sb, Bi, C, Si, Ge, Sn, Pb, and B. Occasionally, anonmetal element can also refer to certain metalloids (e.g., B, Si, Ge,As, Sb, Te, and Po) in Groups 13-17. In one embodiment, the nonmetalelements can include B, Si, C, P, or combinations thereof. Accordingly,for example, the alloy can comprise a boride, a carbide, or both.

A transition metal element can be any of scandium, titanium, vanadium,chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium,zirconium, niobium, molybdenum, technetium, ruthenium, rhodium,palladium, silver, cadmium, hafnium, tantalum, tungsten, rhenium,osmium, iridium, platinum, gold, mercury, rutherfordium, dubnium,seaborgium, bohrium, hassium, meitnerium, ununnilium, unununium, andununbium. In one embodiment, a BMG containing a transition metal elementcan have at least one of Sc, Y, La, Ac, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo,W, Mn, Tc, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd,and Hg. Depending on the application, any suitable transitional metalelements, or their combinations, can be used. The alloy composition cancomprise multiple transitional metal elements, such as at least two, atleast three, at least four, or more, transitional metal elements.

The presently described alloy or alloy “sample” or “specimen” alloy canhave any shape or size. For example, the alloy can have a shape of aparticulate, which can have a shape such as spherical, ellipsoid,wire-like, rod-like, sheet-like, flake-like, or an irregular shape. Theparticulate can have any size. For example, it can have an averagediameter of between about 1 micron and about 100 microns, such asbetween about 5 microns and about 80 microns, such as between about 10microns and about 60 microns, such as between about 15 microns and about50 microns, such as between about 15 microns and about 45 microns, suchas between about 20 microns and about 40 microns, such as between about25 microns and about 35 microns. For example, in one embodiment, theaverage diameter of the particulate is between about 25 microns andabout 44 microns. In some embodiments, smaller particulates, such asthose in the nanometer range, or larger particulates, such as thosebigger than 100 microns, can be used.

The alloy sample or specimen can also be of a much larger dimension. Forexample, it can be a bulk structural component, such as an ingot,housing/casing of an electronic device or even a portion of a structuralcomponent that has dimensions in the millimeter, centimeter, or meterrange.

Solid Solution

The term “solid solution” refers to a solid form of a solution. The term“solution” refers to a mixture of two or more substances, which may besolids, liquids, gases, or a combination of these. The mixture can behomogeneous or heterogeneous. The term “mixture” is a composition of twoor more substances that are combined with each other and are generallycapable of being separated. Generally, the two or more substances arenot chemically combined with each other.

Alloy

In some embodiments, the alloy composition described herein can be fullyalloyed. In one embodiment, an “alloy” refers to a homogeneous mixtureor solid solution of two or more metals, the atoms of one replacing oroccupying interstitial positions between the atoms of the other; forexample, brass is an alloy of zinc and copper. An alloy, in contrast toa composite, can refer to a partial or complete solid solution of one ormore elements in a metal matrix, such as one or more compounds in ametallic matrix. The term alloy herein can refer to both a completesolid solution alloy that can give single solid phase microstructure anda partial solution that can give two or more phases. An alloycomposition described herein can refer to one comprising an alloy or onecomprising an alloy-containing composite.

Thus, a fully alloyed alloy can have a homogenous distribution of theconstituents, be it a solid solution phase, a compound phase, or both.The term “fully alloyed” used herein can account for minor variationswithin the error tolerance. For example, it can refer to at least 90%alloyed, such as at least 95% alloyed, such as at least 99% alloyed,such as at least 99.5% alloyed, such as at least 99.9% alloyed. Thepercentage herein can refer to either volume percent or weightpercentage, depending on the context. These percentages can be balancedby impurities, which can be in terms of composition or phases that arenot a part of the alloy.

Amorphous or Non-Crystalline Solid

An “amorphous” or “non-crystalline solid” is a solid that lacks latticeperiodicity, which is characteristic of a crystal. As used herein, an“amorphous solid” includes “glass” which is an amorphous solid thatsoftens and transforms into a liquid-like state upon heating through theglass transition. Generally, amorphous materials lack the long-rangeorder characteristic of a crystal, though they can possess someshort-range order at the atomic length scale due to the nature ofchemical bonding. The distinction between amorphous solids andcrystalline solids can be made based on lattice periodicity asdetermined by structural characterization techniques such as x-raydiffraction and transmission electron microscopy.

The terms “order” and “disorder” designate the presence or absence ofsome symmetry or correlation in a many-particle system. The terms“long-range order” and “short-range order” distinguish order inmaterials based on length scales.

The strictest form of order in a solid is lattice periodicity: a certainpattern (the arrangement of atoms in a unit cell) is repeated again andagain to form a translationally invariant tiling of space. This is thedefining property of a crystal. Possible symmetries have been classifiedin 14 Bravais lattices and 230 space groups.

Lattice periodicity implies long-range order. If only one unit cell isknown, then by virtue of the translational symmetry it is possible toaccurately predict all atomic positions at arbitrary distances. Theconverse is generally true, except, for example, in quasi-crystals thathave perfectly deterministic tilings but do not possess latticeperiodicity.

Long-range order characterizes physical systems in which remote portionsof the same sample exhibit correlated behavior. This can be expressed asa correlation function, namely the spin-spin correlation function:G(x,x′)=

s(x),s(x′)

.

In the above function, s is the spin quantum number and x is thedistance function within the particular system. This function is equalto unity when x=x″ and decreases as the distance |x−x′| increases.Typically, it decays exponentially to zero at large distances, and thesystem is considered to be disordered. If, however, the correlationfunction decays to a constant value at large |x−x′|, then the system canbe said to possess long-range order. If it decays to zero as a power ofthe distance, then it can be called quasi-long-range order. Note thatwhat constitutes a large value of |x−x′| is relative.

A system can be said to present quenched disorder when some parametersdefining its behavior are random variables that do not evolve with time(i.e., they are quenched or frozen)—e.g., spin glasses. It is oppositeto annealed disorder, where the random variables are allowed to evolvethemselves. Embodiments herein include systems comprising quencheddisorder.

The alloy described herein can be crystalline, partially crystalline,amorphous, or substantially amorphous. For example, the alloysample/specimen can include at least some crystallinity, withgrains/crystals having sizes in the nanometer and/or micrometer ranges.Alternatively, the alloy can be substantially amorphous, such as fullyamorphous. In one embodiment, the alloy composition is at leastsubstantially not amorphous, such as being substantially crystalline,such as being entirely crystalline.

In one embodiment, the presence of a crystal or a plurality of crystalsin an otherwise amorphous alloy can be construed as a “crystallinephase” therein. The degree of crystallinity (or “crystallinity” forshort in some embodiments) of an alloy can refer to the amount of thecrystalline phase present in the alloy. The degree can refer to, forexample, a fraction of crystals present in the alloy. The fraction canrefer to volume fraction or weight fraction, depending on the context. Ameasure of how “amorphous” an amorphous alloy is can be amorphicity.Amorphicity can be measured in terms of a degree of crystallinity. Forexample, in one embodiment, an alloy having a low degree ofcrystallinity can be said to have a high degree of amorphicity. In oneembodiment, for example, an alloy having 60 vol % crystalline phase canhave a 40 vol % amorphous phase.

Amorphous Alloy or Amorphous Metal

An “amorphous alloy” is an alloy having an amorphous content of morethan 50% by volume, preferably more than 90% by volume of amorphouscontent, more preferably more than 95% by volume of amorphous content,and most preferably more than 99% to almost 100% by volume of amorphouscontent. Note that, as described above, an alloy high in amorphicity isequivalently low in degree of crystallinity An “amorphous metal” is anamorphous metal material with a disordered atomic-scale structure. Incontrast to most metals, which are crystalline and therefore have ahighly ordered arrangement of atoms, amorphous alloys arenon-crystalline. Materials in which such a disordered structure isproduced directly from the liquid state during cooling are sometimesreferred to as “glasses.” Accordingly, amorphous metals are commonlyreferred to as “metallic glasses” or “glassy metals.” In one embodiment,a bulk metallic glass (“BMG”) can refer to an alloy, of which themicrostructure is at least partially amorphous. However, there areseveral ways besides extremely rapid cooling to produce amorphousmetals, including physical vapor deposition, solid-state reaction, ionirradiation, melt spinning, and mechanical alloying. Amorphous alloyscan be a single class of materials, regardless of how they are prepared.

Amorphous metals can be produced through a variety of quick-coolingmethods. For instance, amorphous metals can be produced by sputteringmolten metal onto a spinning metal disk. The rapid cooling, on the orderof millions of degrees a second, can be too fast for crystals to form,and the material is thus “locked in” a glassy state. Also, amorphousmetals/alloys can be produced with critical cooling rates low enough toallow formation of amorphous structures in thick layers—e.g., bulkmetallic glasses.

The terms “bulk metallic glass” (“BMG”), bulk amorphous alloy (“BAA”),and bulk solidifying amorphous alloy are used interchangeably herein.They refer to amorphous alloys having the smallest dimension at least inthe millimeter range. For example, the dimension can be at least about0.5 mm, such as at least about 1 mm, such as at least about 2 mm, suchas at least about 4 mm, such as at least about 5 mm, such as at leastabout 6 mm, such as at least about 8 mm, such as at least about 10 mm,such as at least about 12 mm Depending on the geometry, the dimensioncan refer to the diameter, radius, thickness, width, length, etc. A BMGcan also be a metallic glass having at least one dimension in thecentimeter range, such as at least about 1.0 cm, such as at least about2.0 cm, such as at least about 5.0 cm, such as at least about 10.0 cm.In some embodiments, a BMG can have at least one dimension at least inthe meter range. A BMG can take any of the shapes or forms describedabove, as related to a metallic glass. Accordingly, a BMG describedherein in some embodiments can be different from a thin film made by aconventional deposition technique in one important aspect—the former canbe of a much larger dimension than the latter.

Amorphous metals can be an alloy rather than a pure metal. The alloysmay contain atoms of significantly different sizes, leading to low freevolume (and therefore having viscosity up to orders of magnitude higherthan other metals and alloys) in a molten state. The viscosity preventsthe atoms from moving enough to form an ordered lattice. The materialstructure may result in low shrinkage during cooling and resistance toplastic deformation. The absence of grain boundaries, the weak spots ofcrystalline materials in some cases, may, for example, lead to betterresistance to wear and corrosion. In one embodiment, amorphous metals,while technically glasses, may also be much tougher and less brittlethan oxide glasses and ceramics.

Thermal conductivity of amorphous materials may be lower than that oftheir crystalline counterparts. To achieve formation of an amorphousstructure even during slower cooling, the alloy may be made of three ormore components, leading to complex crystal units with higher potentialenergy and lower probability of formation. The formation of amorphousalloy can depend on several factors: the composition of the componentsof the alloy; the atomic radius of the components (preferably with asignificant difference of over 12% to achieve high packing density andlow free volume); and the negative heat of mixing the combination ofcomponents, inhibiting crystal nucleation and prolonging the time themolten metal stays in a supercooled state. However, as the formation ofan amorphous alloy is based on many different variables, it can bedifficult to make a prior determination of whether an alloy compositionwould form an amorphous alloy.

Amorphous alloys, for example, of boron, silicon, phosphorus, and otherglass formers with magnetic metals (iron, cobalt, nickel) may bemagnetic, with low coercivity and high electrical resistance. The highresistance leads to low losses by eddy currents when subjected toalternating magnetic fields, a property useful, for example, astransformer magnetic cores.

Amorphous alloys may have a variety of potentially useful properties. Inparticular, they tend to be stronger than crystalline alloys of similarchemical composition, and they can sustain larger reversible (“elastic”)deformations than crystalline alloys. Amorphous metals derive theirstrength directly from their non-crystalline structure, which can havenone of the defects (such as dislocations) that limit the strength ofcrystalline alloys. For example, one modern amorphous metal, known asVitreloy™, has a tensile strength that is almost twice that ofhigh-grade titanium. In some embodiments, metallic glasses at roomtemperature are not ductile and tend to fail suddenly when loaded intension, which limits the material applicability in reliability-criticalapplications, as the impending failure is not evident. Therefore, toovercome this challenge, metal matrix composite materials having ametallic glass matrix containing dendritic particles or fibers of aductile crystalline metal can be used. Alternatively, a BMG low inelement(s) that tend to cause embitterment (e.g., Ni) can be used. Forexample, a Ni-free BMG can be used to improve the ductility of the BMG.

Another useful property of bulk amorphous alloys is that they can betrue glasses; in other words, they can soften and flow upon heating.This can allow for easy processing, such as by injection molding, inmuch the same way as polymers. As a result, amorphous alloys can be usedfor making sports equipment, medical devices, electronic components andequipment, and thin films. Thin films of amorphous metals can bedeposited as protective coatings via a high velocity oxygen fueltechnique.

A material can have an amorphous phase, a crystalline phase, or both.The amorphous and crystalline phases can have the same chemicalcomposition and differ only in the microstructure—i.e., one amorphousand the other crystalline. Microstructure in one embodiment refers tothe structure of a material as revealed by a microscope at 25×magnification or higher. Alternatively, the two phases can havedifferent chemical compositions and microstructures. For example, acomposition can be partially amorphous, substantially amorphous, orcompletely amorphous.

As described above, the degree of amorphicity (and conversely the degreeof crystallinity) can be measured by fraction of crystals present in thealloy. The degree can refer to volume fraction of weight fraction of thecrystalline phase present in the alloy. A partially amorphouscomposition can refer to a composition of at least about 5 vol % ofwhich is of an amorphous phase, such as at least about 10 vol %, such asat least about 20 vol %, such as at least about 40 vol %, such as atleast about 60 vol %, such as at least about 80 vol %, such as at leastabout 90 vol %. The terms “substantially” and “about” have been definedelsewhere in this application. Accordingly, a composition that is atleast substantially amorphous can refer to one of which at least about90 vol % is amorphous, such as at least about 95 vol %, such as at leastabout 98 vol %, such as at least about 99 vol %, such as at least about99.5 vol %, such as at least about 99.8 vol %, such as at least about99.9 vol %. In one embodiment, a substantially amorphous composition canhave some incidental, insignificant amount of crystalline phase presenttherein.

In one embodiment, an amorphous alloy composition can be homogeneouswith respect to the amorphous phase. A substance that is uniform incomposition is homogeneous. This is in contrast to a substance that isheterogeneous. The term “composition” refers to the chemical compositionand/or microstructure in the substance. A substance is homogeneous whena volume of the substance is divided in half and both halves havesubstantially the same composition. For example, a particulatesuspension is homogeneous when a volume of the particulate suspension isdivided in half and both halves have substantially the same volume ofparticles. However, it might be possible to see the individual particlesunder a microscope. Another example of a homogeneous substance is airwhere different ingredients therein are equally suspended, though theparticles, gases and liquids in air can be analyzed separately orseparated from air.

A composition that is homogeneous with respect to an amorphous alloy canrefer to one having an amorphous phase substantially uniformlydistributed throughout its microstructure. In other words, thecomposition macroscopically comprises a substantially uniformlydistributed amorphous alloy throughout the composition. In analternative embodiment, the composition can be of a composite, having anamorphous phase having therein a non-amorphous phase. The non-amorphousphase can be a crystal or a plurality of crystals. The crystals can bein the form of particulates of any shape, such as spherical, ellipsoid,wire-like, rod-like, sheet-like, flake-like, or an irregular shape. Inone embodiment, it can have a dendritic form. For example, an at leastpartially amorphous composite composition can have a crystalline phasein the shape of dendrites dispersed in an amorphous phase matrix; thedispersion can be uniform or non-uniform, and the amorphous phase andthe crystalline phase can have the same or a different chemicalcomposition. In one embodiment, they have substantially the samechemical composition. In another embodiment, the crystalline phase canbe more ductile than the BMG phase.

The methods described herein can be applicable to any type of amorphousalloy. Similarly, the amorphous alloy described herein as a constituentof a composition or article can be of any type. The amorphous alloy cancomprise the element Zr, Hf, Ti, Cu, Ni, Pt, Pd, Fe, Mg, Au, La, Ag, Al,Mo, Nb, Be, or combinations thereof. Namely, the alloy can include anycombination of these elements in its chemical formula or chemicalcomposition. The elements can be present at different weight or volumepercentages. For example, an iron “based” alloy can refer to an alloyhaving a non-insignificant weight percentage of iron present therein,the weight percent can be, for example, at least about 20 wt %, such asat least about 40 wt %, such as at least about 50 wt %, such as at leastabout 60 wt %, such as at least about 80 wt %. Alternatively, in oneembodiment, the above-described percentages can be volume percentages,instead of weight percentages. Accordingly, an amorphous alloy can bezirconium-based, titanium-based, platinum-based, palladium-based,gold-based, silver-based, copper-based, iron-based, nickel-based,aluminum-based, molybdenum-based, and the like. The alloy can also befree of any of the aforementioned elements to suit a particular purpose.For example, in some embodiments, the alloy, or the compositionincluding the alloy, can be substantially free of nickel, aluminum,titanium, beryllium, or combinations thereof. In one embodiment, thealloy or the composite is completely free of nickel, aluminum, titanium,beryllium, or combinations thereof.

For example, the amorphous alloy can have the formula (Zr, Ti)_(b)(Ni,Cu, Fe)_(b)(Be, Al, Si, B)_(c), wherein a, b, and c each represents aweight or atomic percentage. In one embodiment, a is in the range offrom 30 to 75, b is in the range of from 5 to 60, and c is in the rangeof from 0 to 50 in atomic percentages. Alternatively, the amorphousalloy can have the formula (Zr, Ti)_(b)(Ni, Cu)_(b)(Be)_(c), wherein a,b, and c each represents a weight or atomic percentage. In oneembodiment, a is in the range of from 40 to 75, b is in the range offrom 5 to 50, and c is in the range of from 5 to 50 in atomicpercentages. The alloy can also have the formula (Zr, Ti)_(b)(Ni,Cu)_(b)(Be)_(c), wherein a, b, and c each represents a weight or atomicpercentage. In one embodiment, a is in the range of from 45 to 65, b isin the range of from 7.5 to 35, and c is in the range of from 10 to 37.5in atomic percentages. Alternatively, the alloy can have the formula(Zr)_(a)(Nb, Ti)_(b)(Ni, Cu)_(c)(Al)_(d), wherein a, b, c, and d eachrepresents a weight or atomic percentage. In one embodiment, a is in therange of from 45 to 65, b is in the range of from 0 to 10, c is in therange of from 20 to 40 and d is in the range of from 7.5 to 15 in atomicpercentages. One exemplary embodiment of the aforedescribed alloy systemis a Zr—Ti—Ni—Cu—Be based amorphous alloy under the trade name Vitreloy™such as Vitreloy-1 and Vitreloy-101, as fabricated by LiquidmetalTechnologies, CA, USA. Some examples of amorphous alloys of thedifferent systems are provided in Table 1.

The amorphous alloys can also be ferrous alloys, such as (Fe, Ni, Co)based alloys. Examples of such compositions are disclosed in U.S. Pat.Nos. 6,325,868; 5,288,344; 5,368,659; 5,618,359; and U.S. Pat. No.5,735,975, Inoue et al., Appl. Phys. Lett., Volume 71, p 464 (1997),Shen et al., Mater. Trans., JIM, Volume 42, p 2136 (2001), and JapanesePatent Application No. 200126277 (Pub. No. 2001303218 A). One exemplarycomposition is Fe₇₂Al₅Ga₂P₁₁C₆B₄. Another example isFe₇₂Al₇Zr₁₀Mo₅W₂B₁₅. Another iron-based alloy system that can be used inthe coating herein is disclosed in U.S. Patent Application PublicationNo. 2010/0084052, wherein the amorphous metal contains, for example,manganese (1 to 3 atomic %), yttrium (0.1 to 10 atomic %), and silicon(0.3 to 3.1 atomic %) in the range of composition given in parentheses;and that contains the following elements in the specified range ofcomposition given in parentheses: chromium (15 to 20 atomic %),molybdenum (2 to 15 atomic %), tungsten (1 to 3 atomic %), boron (5 to16 atomic %), carbon (3 to 16 atomic %), and the balance iron.

The aforedescribed amorphous alloy systems can further includeadditional elements, such as additional transition metal elements,including Nb, Cr, V, and Co. The additional elements can be present atless than or equal to about 30 wt %, such as less than or equal to about20 wt %, such as less than or equal to about 10 wt %, such as less thanor equal to about 5 wt %. In one embodiment, the additional, optionalelement is at least one of cobalt, manganese, zirconium, tantalum,niobium, tungsten, yttrium, titanium, vanadium and hafnium to formcarbides and further improve wear and corrosion resistance. Furtheroptional elements may include phosphorous, germanium and arsenic,totaling up to about 2%, and preferably less than 1%, to reduce meltingpoint. Otherwise incidental impurities should be less than about 2% andpreferably 0.5%.

TABLE 1 Exemplary amorphous alloy compositions Alloy Atm % Atm % Atm %Atm % Atm % Atm % 1 Zr Ti Cu Ni Be 41.20% 13.80% 12.50% 10.00% 22.50% 2Zr Ti Cu Ni Be 44.00% 11.00% 10.00% 10.00% 25.00% 3 Zr Ti Cu Ni Nb Be56.25% 11.25%  6.88%  5.63%  7.50% 12.50% 4 Zr Ti Cu Ni Al Be 64.75% 5.60% 14.90% 11.15%  2.60%  1.00% 5 Zr Ti Cu Ni Al 52.50%  5.00% 17.90%14.60% 10.00% 6 Zr Nb Cu Ni Al 57.00%  5.00% 15.40% 12.60% 10.00% 7 ZrCu Ni Al Sn 50.75% 36.23%  4.03%  9.00%  0.50% 8 Zr Ti Cu Ni Be 46.75% 8.25%  7.50% 10.00% 27.50% 9 Zr Ti Ni Be 21.67% 43.33%  7.50% 27.50% 10Zr Ti Cu Be 35.00% 30.00%  7.50% 27.50% 11 Zr Ti Co Be 35.00% 30.00% 6.00% 29.00% 12 Au Ag Pd Cu Si 49.00%  5.50%  2.30% 26.90% 16.30% 13 AuAg Pd Cu Si 50.90%  3.00%  2.30% 27.80% 16.00% 14 Pt Cu Ni P 57.50%14.70%  5.30% 22.50% 15 Zr Ti Nb Cu Be 36.60% 31.40%  7.00%  5.90%19.10% 16 Zr Ti Nb Cu Be 38.30% 32.90%  7.30%  6.20% 15.30% 17 Zr Ti NbCu Be 39.60% 33.90%  7.60%  6.40% 12.50% 18 Cu Ti Zr Ni 47.00% 34.00%11.00%  8.00% 19 Zr Co Al 55.00% 25.00% 20.00%

In some embodiments, a composition having an amorphous alloy can includea small amount of impurities. The impurity elements can be intentionallyadded to modify the properties of the composition, such as improving themechanical properties (e.g., hardness, strength, fracture mechanism,etc.) and/or improving the corrosion resistance. Alternatively, theimpurities can be present as inevitable, incidental impurities, such asthose obtained as a byproduct of processing and manufacturing. Theimpurities can be less than or equal to about 10 wt %, such as about 5wt %, such as about 2 wt %, such as about 1 wt %, such as about 0.5 wt%, such as about 0.1 wt %. In some embodiments, these percentages can bevolume percentages instead of weight percentages. In one embodiment, thealloy sample/composition consists essentially of the amorphous alloy(with only a small incidental amount of impurities). In anotherembodiment, the composition includes the amorphous alloy (with noobservable trace of impurities).

In one embodiment, the final parts exceeded the critical castingthickness of the bulk solidifying amorphous alloys.

In embodiments herein, the existence of a supercooled liquid region inwhich the bulk-solidifying amorphous alloy can exist as a high viscousliquid allows for superplastic forming. Large plastic deformations canbe obtained. The ability to undergo large plastic deformation in thesupercooled liquid region is used for the forming and/or cuttingprocess. As oppose to solids, the liquid bulk solidifying alloy deformslocally which drastically lowers the required energy for cutting andforming. The ease of cutting and forming depends on the temperature ofthe alloy, the mold, and the cutting tool. As higher is the temperature,the lower is the viscosity, and consequently easier is the cutting andforming.

Embodiments herein can utilize a thermoplastic-forming process withamorphous alloys carried out between Tg and Tx, for example. Herein, Txand Tg are determined from standard DSC measurements at typical heatingrates (e.g. 20° C./min) as the onset of crystallization temperature andthe onset of glass transition temperature.

The amorphous alloy components can have the critical casting thicknessand the final part can have thickness that is thicker than the criticalcasting thickness. Moreover, the time and temperature of the heating andshaping operation is selected such that the elastic strain limit of theamorphous alloy could be substantially preserved to be not less than1.0%, and preferably not being less than 1.5%. In the context of theembodiments herein, temperatures around glass transition means theforming temperatures can be below glass transition, at or around glasstransition, and above glass transition temperature, but preferably attemperatures below the crystallization temperature T_(x). The coolingstep is carried out at rates similar to the heating rates at the heatingstep, and preferably at rates greater than the heating rates at theheating step. The cooling step is also achieved preferably while theforming and shaping loads are still maintained.

Electronic Devices

The embodiments herein can be valuable in the fabrication of electronicdevices using a BMG. An electronic device herein can refer to anyelectronic device known in the art. For example, it can be a telephone,such as a cell phone, and a land-line phone, or any communicationdevice, such as a smart phone, including, for example an iPhone™, and anelectronic email sending/receiving device. It can be a part of adisplay, such as a digital display, a TV monitor, an electronic-bookreader, a portable web-browser (e.g., iPad™), and a computer monitor. Itcan also be an entertainment device, including a portable DVD player,conventional DVD player, Blue-Ray disk player, video game console, musicplayer, such as a portable music player (e.g., iPod™), etc. It can alsobe a part of a device that provides control, such as controlling thestreaming of images, videos, sounds (e.g., Apple TV™), or it can be aremote control for an electronic device. It can be a part of a computeror its accessories, such as the hard drive tower housing or casing,laptop housing, laptop keyboard, laptop track pad, desktop keyboard,mouse, and speaker. The article can also be applied to a device such asa watch or a clock.

Molding/Casting and Separating of Bulk-Solidifying Amorphous Alloys

In one embodiment, the final parts exceeded the critical castingthickness of the bulk solidifying amorphous alloys.

In another embodiment, hot forming and hot separating can be performedin any order or exclusively.

In another embodiment, the bulk-solidifying amorphous alloy or compositecontaining amorphous alloy, the mold, and the cutting tool are at thecutting temperature in the supercooled liquid region.

In still another embodiment, the bulk-solidifying amorphous alloy orcomposite containing amorphous alloy, the mold, and the cutting tool areat the cutting temperature in the supercooled liquid region. A wire isused as a cutting tool.

In still another embodiment, the bulk-solidifying amorphous alloy orcomposite containing amorphous alloy, the mold, and the cutting tool areat the cutting temperature in the supercooled liquid region. The cuttingtool is a blade.

In still another embodiment, the bulk-solidifying amorphous alloy, themold, and the cutting tool are at the cutting temperature in thesupercooled liquid region. The cutting is performed by shearing twosurfaces against each other. The bulk solidifying alloy or compositecontaining amorphous alloy is connected to one of the surfaces.

In still another embodiment, the bulk-solidifying amorphous alloy orcomposite containing amorphous alloy is heated locally, where the cut isperformed, to the cutting temperature and the bulk solidifying alloy canbe at any temperature.

In still another embodiment, the bulk-solidifying amorphous alloy orcomposite containing amorphous alloy is heated locally, where the cut isperformed, to the cutting temperature, and the bulk solidifying alloycan be at any temperature. A heated wire which is at the cuttingtemperature is used as a cutting tool.

In still another embodiment, the bulk-solidifying amorphous alloy orcomposite containing amorphous alloy is heated locally, where the cut isperformed, to the cutting temperature, and the bulk solidifying alloycan be at any temperature. A heated plate which is at the cuttingtemperature is used as a cutting tool.

In still another embodiment, the bulk-solidifying amorphous alloy orcomposite containing amorphous alloy is heated locally, where the cut isperformed, to the cutting temperature, and the bulk solidifying alloy orcomposite containing amorphous alloy can be at any temperature. Thecutting is performed by shearing two heated surfaces against each other.

In still another embodiment, the cutting is performed to separate thereservoir containing feedstock and the part.

In still another embodiment, the purpose of the cutting is to provide adesired shape where the bulk solidifying alloy or composite containingamorphous alloy has been formed into the mold cavity.

In still another embodiment, the purpose of the cutting is to provide adesired stock material where the bulk solidifying alloy or compositecontaining amorphous alloy will be formed into the mold cavity.

In another embodiment, the bulk amorphous alloy or composite containingamorphous alloy, in the supercooled liquid region, is pushed into a moldcavity, also heated to within the supercooled liquid region.

In another embodiment, the bulk amorphous alloy or composite containingamorphous alloy, in the supercooled liquid region, is pushed into a moldcavity, which is heated to below the supercooled liquid region.

In another embodiment, the bulk amorphous alloy or composite containingamorphous alloy is heated by a laser, a resistant furnace or alike, orinductively.

In another embodiment, the mold can also act as a cutting tool.

In another embodiment, the bulk amorphous alloy or composite containingamorphous alloy is heated by the plunger and/or the mold to withinsupercooled liquid region.

In one embodiment of the method of forming and separating, the providedbulk solidifying amorphous alloy composition is Zr/Ti base.

In one embodiment of the method of forming and separating, the providedbulk solidifying amorphous alloy composition is Zr-base.

In one embodiment of the method of forming and separating, the providedbulk solidifying amorphous alloy composition is Zr/Ti base with no Ni.

In one embodiment of the method of forming and separating, the providedbulk solidifying amorphous alloy composition is Zr/Ti base with no Al.

In one embodiment of the method of forming and separating, the providedbulk solidifying amorphous alloy composition is Zr/Ti base with no Be.

In one embodiment of the method of forming and separating, the providedbulk solidifying amorphous alloy composition is Cu base.

In one embodiment of the method of forming and separating, the providedbulk solidifying amorphous alloy composition is Fe base.

In one embodiment of the method of forming and separating, thebulk-solidifying amorphous alloy or composite containing amorphous alloyis formed and/or separated into a net shape part under vacuum.

In one embodiment of the method of forming and separating, thebulk-solidifying amorphous alloy or composite containing amorphous alloyis formed and/or separated into a net shape part under inert atmosphere.

In one embodiment of the method of forming and separating, thebulk-solidifying amorphous alloy or composite containing amorphous alloyis formed and/or separated into a net shape part under partial vacuum.

In one embodiment of the method of forming and separating, thebulk-solidifying amorphous alloy or composite containing amorphous alloycan be formed and/or separated one or more times.

In embodiments herein, the existence of a supercooled liquid region inwhich the bulk-solidifying amorphous alloy can exist as a high viscousliquid allows for superplastic forming. Large plastic deformations canbe obtained. The ability to undergo large plastic deformation in thesupercooled liquid region is used for the forming and/or cuttingprocess. As oppose to solids, the liquid bulk solidifying alloy deformslocally which drastically lowers the required energy for cutting andforming. The ease of cutting and forming depends on the temperature ofthe alloy, the mold, and the cutting tool. As higher is the temperature,the lower is the viscosity, and consequently easier is the cutting andforming.

The cutting and forming processes can be carried out on a sample that isat uniform temperature at the cutting temperature where also the cuttingtool is at the cutting temperature. This is however not necessary.Alternatively, the sample temperature varies and is only locally at thecutting temperature where the cut is performed. This can be either doneby locally heating it or alternatively by heating the cutting tool orthe mold. On the other hand, the forming process should be carried outon a sample that is at uniform temperature and the mold must be heatedto the alloy's supercooled liquid region or lower to obtain a desiredforming and cooling performance.

Herein, Tx and Tg are determined from standard DSC (DifferentialScanning calorimetry) measurements at typical heating rates (e.g. 20°C./min) as the onset of crystallization temperature and the onset ofglass transition temperature.

The feedstock can have the critical casting thickness and the final partcan have thickness that is thicker than the critical casting thickness.Moreover, the time and temperature of the heating and shaping operationis selected such that the elastic strain limit of the amorphous alloy issubstantially preserved to be not less than 1.0%, and preferably notbeing less than 1.5%. In the context of the embodiments herein,temperatures around glass transition means the forming temperatures canbe below glass transition, at or around glass transition, and aboveglass transition temperature, but preferably at temperatures below thecrystallization temperature T_(x). The cooling step is carried out atrates similar to the heating rates at the heating step, and preferablyat rates greater than the heating rates at the heating step. The coolingstep is also achieved preferably while the forming and shaping loads arestill maintained.

In one embodiment, one would heat a BMG alloy that is already in a formof an amorphous alloy from room temperature to a temperature between Tgand Tx and force the heated BMG alloy it into a mold having the shape ofthe part one wants to form. However, after injecting the BMG alloy intothe mold, one would not cool the part down to room temperature. Instead,one could cool the BMG part down to below Tg or slightly above Tg. Onecan then apply the hot cutting tool heated to a temperature between Tgand Tx and shear the gate off the BMG part and subsequently cool the BMGpart down further to below Tg (e.g., near room temperature). In short,in this embodiment, one could start with an amorphous BMG alloy which isbelow Tg, raise the temperature of the BMG alloy to above Tg, mold theBMG alloy into a molded part, lower the temperature of the molded partto below Tg or slightly above Tg, and cut portions of the molded partusing a hot cutting tool heated to above Tg, at a temperature in thesupercooled liquid region of the BMG alloy in between Tg and Tx. Thetemperature of the molded part as a whole could be during cutting couldbe below Tg or above Tg, but a localized temperature in the cutting zonesurrounding the hot knife has to be above Tg.

In another embodiment, one could take a BMG alloy in a molten form at atemperature above Tm, cast or mold the molten BMG alloy into the shapeof a BMG part at a temperature above Tg, and then cool the BMG part tobelow Tg such that the BMG part is amorphous substantially throughoutthe BMG part. Then, one could either locally heat a region the BMG partwhere one would be cutting the BMG part to a temperature above Tg orheat the whole BMG part to above Tg and cut a portion of the BMG part.

In one variation, one could have different texture or different featureson the knife, and when one cuts the BMG part, the texture or featureswill be replicated on the BMG part. With conventional water jet or sawcuts, one needs to do finishing after cutting. For example, one needs toundertake post-process finishing such as grinding down the BMG part,shaving it or chamfering it. By using the hot knife to cut the BMG part,one could incorporate these features into the knife and when one cutsthe BMG part using the hot knife without undertaking post-processfinishing.

Furthermore, by the embodiments herein, one can make a clean cut withoutcausing localized heating and crystallization in a region near to thecutting surface as one would normally expect using saw cutting of a BMGpart.

One exemplary method of forming and separating bulk solidifyingamorphous alloy comprises the following steps:

-   -   1) Providing a feedstock of amorphous alloy being substantially        amorphous.    -   2) Heating the feedstock, the mold, and the cutting tool to        around the glass transition temperature or within the        supercooled liquid region;    -   3) Shaping the heated feedstock into the mold and separate any        excess material to form the desired shape; and    -   4) Cooling the formed part to temperatures far below the glass        transition temperature.

More specifically, the above exemplary method of forming and separatingbulk solidifying amorphous alloy could be carried out with reference toFIGS. 3( a) and 3(b) as follows:

(1) Obtain a bulk amorphous alloy feedstock and heat it to between Tgand Tx.(2) Insert (inject) the heated bulk amorphous alloy into a mold to forma BMG part(3) Activate a cutter, which is at a temperature between Tg and Tx, totrim the BMG part. The BMG part may be below Tg during cutting or theBMG part may be between Tg and Tx. The BMG part may be cooled whilecutting.(4) Open the mold and eject the trimmed BMG part. The BMG part may becooled during ejection.

Another exemplary method of forming and separating bulk solidifyingamorphous alloy comprises the following steps:

-   -   1. Providing a homogeneous alloy feedstock of amorphous alloy        (not necessarily amorphous);    -   2. Heating the feedstock to a casting temperature above the        melting temperatures;    -   3. Introducing the molten alloy into a first mold with critical        casting thickness or thinner; and quenching the molten alloy to        temperatures below glass transition.    -   4. Heating the feedstock, the second mold, and the cutting tool        to around the glass transition temperature or within the        supercooled liquid region;    -   5. Shaping the heated feedstock into the second mold and        separate any excess material to form a desired shape; and    -   6. Cooling the formed part to temperatures far below the glass        transition temperature. The part may have thickness thicker than        the critical casting thickness.    -   7. A second mold may not be needed, i.e., everything can be        incorporated into one mold.

More specifically, the above exemplary method of forming and separatingbulk solidifying amorphous alloy could be carried out with reference toFIGS. 3( a) and 3(b) as follows:

(1) Obtain metal alloy feedstock that may or may not be amorphous andheat to above Tm.(2) Insert (inject) the molten feedstock in a mold shaped in the form apart.(3) Cool the molten feedstock in the mold to below Tg to form a BMGpart.(4) Activate a cutter, which is at a temperature between Tg and Tx, totrim the BMG part. The BMG part may be below Tg during cutting or theBMG part may be between Tg and Tx. The BMG part may be cooled whilecutting.(5) Open the mold and eject the trimmed BMG part. The BMG part may becooled during ejection.Forming Microfeatures while Separating of Bulk-Solidifying AmorphousAlloys

Other embodiments relate to apparatus for molding/casting a BMG part andcutting portion of the BMG part using a hot knife. The knife ismaintained at heated temperature above Tg and can have different typesof microfeatures on it that create similar microfeatures on the BMG partas it is being cut.

The microfeatures could comprise holographic logos. This could beaccomplished with the knife having a negative image of the hologram andwhile one is cutting the BMG part, one would create a hologram on theBMG part in situ in one step along with cutting of the BMG part as shownin FIGS. 4( a) and 4(b). To avoid smearing the hologram, the knife couldhave a slight draft angle so that when one removes the knife, it doesnot smear the microfeatures formed on the BMG part as when one removesthe knife one would form a little chamfer that will hold on to the shapethat one has already formed.

What is claimed:
 1. A method comprising: processing a metal alloy toform a bulk solidifying amorphous alloy part, wherein the processing isperformed in a manner such that a time-temperature profile during theprocessing does not traverse through a region bounding a crystallineregion in a time-temperature-transformation (TTT) diagram of the metalalloy, and cutting a portion of the bulk solidifying amorphous alloypart by a cutting tool that is heated to a temperature greater than aglass transition temperature (Tg) of the metal alloy without previouslycooling the bulk solidifying amorphous alloy part to a temperature nearroom temperature.
 2. The method of claim 1, wherein the processing themetal alloy to form a bulk solidifying amorphous alloy part comprisesheating an amorphous alloy from below Tg to a superplastic formingregion between Tg and a melting point of the metal alloy (Tm), andinserting the amorphous alloy into a mold.
 3. The method of claim 1,wherein the cutting the portion of the bulk solidifying amorphous alloypart by the cutting tool comprises shearing a portion of the bulksolidifying amorphous alloy part.
 4. The method of claim 1, whereinduring the cutting the portion of the bulk solidifying amorphous alloypart by the cutting tool, a temperature of the bulk solidifyingamorphous alloy part is below Tg or above Tg, except that a localizedtemperature in a cutting zone surrounding the cutting tool is above Tg.5. The method of claim 1, wherein the processing the metal alloy to forma bulk solidifying amorphous alloy part comprises heating the metalalloy to Tm or above, inserting the metal alloy into a mold, and coolingthe metal alloy to a temperature below Tg to form the bulk solidifyingamorphous alloy part.
 6. The method of claim 5, wherein the cutting theportion of the bulk solidifying amorphous alloy part by the cutting toolcomprises shearing a portion of the bulk solidifying amorphous alloypart.
 7. The method of claim 6, wherein during the cutting the portionof the bulk solidifying amorphous alloy part by the cutting tool, atemperature of the bulk solidifying amorphous alloy part is below Tg orabove Tg, except that a localized temperature in a cutting zonesurrounding the cutting tool is above Tg.
 8. A method to form and toseparate a bulk solidifying amorphous alloy or a composite containingamorphous alloy comprising a metal alloy, wherein the forming andseparating takes place at a temperature around the glass transitiontemperature or within a supercooled liquid region of the metal alloy. 9.The method of claim 8, wherein the metal alloy is described by thefollowing molecular formula: (Zr, Ti)_(a)(Ni, Cu, Fe)_(b)(Be, Al, Si,B)_(c), wherein “a” is in the range of from 30 to 75, “b” is in therange of from 5 to 60, and “c” is in the range of from 0 to 50 in atomicpercentages.
 10. The method of claim 8, wherein the metal alloy isdescribed by the following molecular formula: (Zr, Ti)_(a)(Ni,Cu)_(b)(Be)_(c), wherein “a” is in the range of from 40 to 75, “b” is inthe range of from 5 to 50, and “c” is in the range of from 5 to 50 inatomic percentages.
 11. The method of claim 8, wherein the bulksolidifying amorphous alloy or composite containing amorphous alloy cansustain strains up to 1.5% or more without any permanent deformation orbreakage.
 12. A method of forming and separating of a bulk solidifyingamorphous alloy or a composite containing amorphous alloy comprising ametal alloy, comprising: providing a feedstock of the bulk solidifyingamorphous alloy or the composite containing amorphous alloy; heating thefeedstock, a mold, and a cutting tool to around a glass transitiontemperature or within a supercooled liquid region of the metal alloy;shaping the heated feedstock into the mold and separating any excessmaterial by the cutting tool to form the desired shape; and cooling theformed part to temperatures far below the glass transition temperature.13. A method of forming and separating of a bulk solidifying amorphousalloy or a composite containing amorphous alloy comprising a metalalloy, comprising: providing the metal alloy; heating the metal alloy toa casting temperature at or above a melting temperature of the metalalloy to form a molten alloy; introducing the molten alloy into a mold;and quenching the molten alloy to a temperature below a glass transitiontemperature of the metal alloy to form the bulk solidifying amorphousalloy or the composite containing amorphous alloy; heating the bulksolidifying amorphous alloy or the composite containing amorphous alloyand a cutting tool to around the glass transition temperature or withina supercooled liquid region of the metal alloy; separating any excessmaterial from the bulk solidifying amorphous alloy or the compositecontaining amorphous alloy to form a part having a desired shape; andcooling the part to temperature below the glass transition temperature.14. The method of claim 8, wherein the separating comprises formingmicrofeatures on a surface of the bulk solidifying amorphous alloy orthe composite containing amorphous alloy.
 15. The method of claim 14,wherein the microfeatures comprise a hologram.
 16. An apparatuscomprising: a mold configured to process a metal alloy to form a bulksolidifying amorphous alloy part, wherein the mold is configured to beheated or cooled in a manner such that a time-temperature profile duringthe metal alloy in the mold does not traverse through a region boundinga crystalline region in a time-temperature-transformation (TTT) diagramof the metal alloy, and a cutting tool configured to cut a portion ofthe bulk solidifying amorphous alloy part, wherein the cutting tool iscapable of being heated to a temperature greater than a glass transitiontemperature (Tg) of the metal alloy and cut the portion of the bulksolidifying amorphous alloy part without previously cooling the bulksolidifying amorphous alloy part to a temperature near room temperature.17. The apparatus of claim 16, wherein the cutting tool comprises amicrofeature on a surface of the cutting tool such that the microfeaturecan be formed on a surface of the bulk solidifying amorphous alloy partafter cutting the portion of the bulk solidifying amorphous alloy part.18. A method of forming and separating of a bulk solidifying amorphousalloy or a composite containing amorphous alloy comprising a metalalloy, comprising: providing the metal alloy; heating the metal alloy toa casting temperature at or above a melting temperature of the metalalloy to form a molten alloy; introducing the molten alloy into a mold;and quenching the molten alloy to a temperature below a glass transitiontemperature of the metal alloy to form the bulk solidifying amorphousalloy or the composite containing amorphous alloy; heating only thecutting tool to around the glass transition temperature or within asupercooled liquid region of the metal alloy while the bulk solidifyingamorphous alloy or the composite containing amorphous alloy is attemperature below Tg; separating any excess material from the bulksolidifying amorphous alloy or the composite containing amorphous alloyto form a part having a desired shape; and cooling the part totemperature below the glass transition temperature.